A vehicle control apparatus which performs an adaptive cruise control and a pre-crash brake control has been conventionally known. Hereinafter, a vehicle in which such a vehicle control apparatus is mounted is referred to as an “own vehicle”.
The adaptive cruise control is a control to make the own vehicle travel at a predetermined constant speed when no preceding vehicle exists ahead of the own vehicle, and when there exists a preceding vehicle, to accelerate or decelerate the own vehicle in such a manner that the own vehicle trails the preceding vehicle, keeping a predetermined inter-vehicular distance. Specifically, in the adaptive cruise control where there exists the preceding vehicle, a target acceleration is calculated based on a “deviation between an inter-vehicular distance to the preceding vehicle and the predetermined inter-vehicular distance” and a “relative speed”, and the own vehicle is accelerated or decelerated so that an acceleration of the own vehicle becomes equal to the target acceleration. Hereinafter, the adaptive cruise control is also referred to as an “ACC”.
On the other hand, the pre-crash brake control is performed by a vehicle control apparatus where a pre-crash safety system (PCS) is adopted. The pre-crash brake control is a control to automatically generate a braking force when there exists a target object with a high probability of colliding with the own vehicle. Specifically, a time-to-collision (TTC) to a target object (a vehicle, a pedestrian, and a bicycle) is calculated based on a distance to this target object and a relative speed, and when the time-to-collision is less than or equal to a time threshold, the braking force is generated. Hereinafter, the pre-crash brake control is also referred to as a “PCBC”.
One of prior art control apparatuses (hereinafter, referred to as a “prior art apparatus”) capable of performing both of the ACC and the PCBC is configured to perform the PCBC in preference to the ACC when a performing condition for the PCBC is satisfied while the ACC is being performed and to cancel (stop) the ACC. That is, when the PCBC is performed while the ACC is being performed, the prior art apparatus is configured to cancel the ACC and thereafter not to resume the ACC automatically after the PCBC is finished (refer to Japanese Patent Application Laid-Open (kokai) No. 2007-223596.). This is because a collision avoidance function by the PCBC should be given priority over a function for reducing a driving load of a driver by the ACC. It should be noted that in the Japanese Patent Application Laid-Open (kokai) No. 2007-223596, the ACC is referred to as a “traveling state control” and the PCBC is referred to as a “collision avoidance control”.